What Does Your User Agent Say About You?


A user agent is a computer program representing a person, for example, a browser in a Web context.

Besides a browser, a user agent could be a bot scraping webpages, a download manager, or another app accessing the Web. Along with each request they make to the server, browsers include a self-identifying User-Agent HTTP header called a user agent (UA) string. This string often identifies the browser, its version number, and its host operating system.

Spam bots, download managers, and some browsers often send a fake UA string to announce themselves as a different client. This is known as user agent spoofing.

The user agent string can be accessed with JavaScript on the client side using the navigator.userAgent property.

A typical user agent string looks like this: "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0".


User Agent String

Browser Data

User Agent Allow

James Lee
• Friday, 30 July, 2021
• 8 min read

Search engines robots are programs that visit your site and follow the links on it to learn about your pages. The best way to edit it is to log in to your web host via a free FTP client like FileZilla, then edit the file with a text editor like Notepad (Windows) or TextEd it (Mac).

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If you don’t know how to login to your server via FTP, contact your web hosting company to ask for instructions. Some plugins, like Yoast SEO, also allow you to edit the robots.txt file from within your WordPress dashboard.

If you want to instruct all robots to stay away from your site, then this is the code you should put in your robots.txt to disallow all: In effect, this will tell all robots and web crawlers that they are not allowed to access or crawl your site.

Important: Disallowing all robots on a live website can lead to your site being removed from search engines and can result in a loss of traffic and revenue. You exclude the files and folders that you don’t want to be accessed, everything else is considered to be allowed.

You simply put a separate line for each file or folder that you want to disallow. The reason for this setting is that Google Search Console used to report an error if it wasn’t able to crawl the admin-ajax.php file.

This sitemap should contain a list of all the pages on your site, so it makes it easier for the web crawlers to find them all. If you want to block your entire site or specific pages from being shown in search engines like Google, then robots.txt is not the best way to do it.

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Search engines can still index files that are blocked by robots, they just won’t show some useful metadata. On WordPress, if you go to Settings Reading and check “Discourage search engines from indexing this site” then a no index tag will be added to all your pages.

In some cases, you may want to block your entire site from being accessed, both by bots and people. Keep in mind that robots can ignore your robots.txt file, especially abusive bots like those run by hackers looking for security vulnerabilities.

Also, if you are trying to hide a folder from your website, then just putting it in the robots.txt file may not be a smart approach. If you want to make sure that your robots.txt file is working, you can use Google Search Console to test it.

Using it can be useful to block certain areas of your website, or to prevent certain bots from crawling your site. If you are going to edit your robots.txt file, then be careful because a small mistake can have disastrous consequences.

For example, if you misplace a single forward slash then it can block all robots and literally remove all of your search traffic until it gets fixed. I have worked with a big site before that once accidentally put a “Disallow: /” into their live robots.txt file.

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The Chrome (or Chromium/Blink-based engines) user agent string is similar to Firefox’s. For compatibility, it adds strings like HTML, like Gecko and Safari.

The Opera browser is also based on the Blink engine, which is why it almost looks the same, but adds “Or/”. In this example, the user agent string is mobile Safari’s version.

Robots.txt is a plain text file that follows the Robots Exclusion Standard. Each rule blocks (or allows) access for a given crawler to a specified file path in that website.

Don't use a word processor; word processors often save files in a proprietary format and can add unexpected characters, such as curly quotes, which can cause problems for crawlers. Use the robots.txt Tester tool to write or edit robots.txt files for your site.

This tool enables you to test the syntax and behavior against your site. The robots.txt file must be located at the root of the website host to which it applies.

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If you're unsure about how to access your website root, or need permissions to do so, contact your web hosting service provider. If you can't access your website root, use an alternative blocking method such as meta tags.

Groups are processed from top to bottom, and a user agent can match only one rule set, which is the first, most-specific rule that matches a given user agent. The default assumption is that a user agent can crawl any page or directory not blocked by a Disallow: rule.

Supports the * wildcard for a path prefix, suffix, or entire string. Supports the * wildcard for a path prefix, suffix, or entire string.

Allow : A directory or page, relative to the root domain, that should be crawled by the user agent just mentioned. Supports the * wildcard for a path prefix, suffix, or entire string.

Please read the full documentation, as the robots.txt syntax has a few tricky parts that are important to learn. Keep in mind that in some situations URLs from the website may still be indexed, even if they haven't been crawled.

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Note: this does not match the various Abbot crawlers, which must be named explicitly. Remember that you shouldn't use robots.txt to block access to private content: use proper authentication instead.

Disallow crawling of a single webpage by listing the page after the slash: This implementation hides your pages from search results, but the Mediapartners-Google web crawler can still analyze them to decide what ads to show visitors to your site.

For instance, the sample code blocks any URLs that end with .xls : There's no “standard” way of writing an user agent string, so different web browsers use different formats (some are wildly different), and many web browsers cram loads of information into their user agents.

Making statements based on opinion; back them up with references or personal experience. The sad reality is that most webmasters have no idea what a robots.txt file is.

A robot in this sense is a “spider.” It’s what search engines use to crawl and index websites on the internet. Once that’s complete, the robot will then move on to external links and continue its indexing.

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This is how search engines find other websites and build such an extensive index of sites. When a search engine (or robot, or spider) hits a site, the first thing it will look for is a robots.txt file.

Remember to keep this file in your root directory. Keeping it in the root directory will ensure that the robot will be able to find the file and use it correctly.

White spaces and comment lines can be used but are not supported by most robots. Notice the “Disallow:” command is blank; this tells robots that nothing is off limits.

It also doesn’t allow the admin.php file to be indexed, which is located in the root directory. This list tells the Google Bot not to index the admin folder.

Just punch in a URL and add robots.txt to the end to find out if a site uses it or not. It will display their robots.txt file in plain text so anyone can read it.

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Password protection with Apache but allow from a user agent | The Electric Toolbox Blog We have had some bad bots using an empty agent string.

The firewall Sergeant Blocking” doesn’t allow an empty string. I made a firewall rule to handle it, but I’d prefer all my agent blocking in the same area.

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